Mom's chocolate frosting

From: Six sisters stuff...
Mom's Chocolate Frosting:

1 stick margarine (1/2 cup), softened
1/4 cup milk
1-2 tsp vanilla (depending on your taste)
3 tablespoons of cocoa
2-3 cups of powdered sugar

Mix all ingredients with a hand mixer until smooth.  Add more powdered sugar or milk until you reach desired consistency and spread on top of bars.

*This is delicious, it's great for frosting cakes, brownies, chocolate cookie filling etc.  So good!